A buck regulator converter such as a semiconductor device may have a structure in which a high-side transistor and a low-side transistor are connected. The buck regulator converter is used to convert a direct-current high-side to a direct-current low-side. For example, field-effect transistors (FET) may be used respectively as the high-side transistor and the low-side transistor. The field-effect transistors (FET) may be high-electron-mobility transistors (HEMT).
Japanese Laid-open Patent Publication No. 2008-187167 discloses that the low-side and high-side driver switches being group-III nitride devices are formed in a semiconductor substrate and a trench insulating from a connection between the low-side and high-side driver switches is formed in the semiconductor substrate. The trench is filled with an insulator. The low-side and high-side driver switches respectively include drain, source and gate electrodes.
Japanese Laid-open Patent Publication No. 2005-203766 discloses that high-side and low-side transistors are formed in different semiconductor substrates, and the transistors are connected by wiring on the semiconductor substrates to obtain a DC-DC converter.
Japanese Laid-open Patent Publication No. 2006-049341 discloses that a non-insulated DC-DC converter in which a high-side transistor and a low-side transistor serially connected and the low-side transistor and a schottky barrier diode connected in parallel to the low-side transistor are formed in an identical semiconductor chip.
The non-insulated DC-DC converter has the schottky barrier diode in the center of the semiconductor chip and the low-side transistor on both sides of the semiconductor chip.
Japanese Laid-open Patent Publication No. 2009-170747 discloses that high-side and low-side transistors for a DC-DC converter are formed in different regions of a silicon substrate. With the structure, a drain region of the low-side transistor is formed on a lower surface side of a silicon substrate and the source region of the high-side transistor is formed on the upper layer of the silicone substrate. The drain region of the low-side transistor and the source region of the high-side transistor are connected via a connection member inside a trench penetrating the semiconductor substrate.